One day, a woman walks into a dentist's office and asks how much it will cost to extract wisdom teeth.
"Eighty dollars," the dentist says.
"That's a ridiculous amount!" the woman says. "Isn't there a cheaper way?"
"Well," the dentist says, "if you don't use an anesthetic, I can knock the price down to $60."
"That's still too expensive," replies the woman.
"Okay," says the dentist. "If I save on anesthesia and simply rip the teeth out with a pair of pliers, I can knock the price down to $20."
"Nope," moans the woman, "it's still too much."
"Well," says the dentist, scratching his head, "if I let one of my students do it, I suppose I can knock the price down to $10."
"Marvelous," says the woman. "May I book my mother-in-law for next Tuesday please?"